Method and apparatus for shape forming endovascular graft material

ABSTRACT

Methods and devices for molding a desired configuration into an endovascular graft section that is made of a plurality of layers of fusible material. Layers of fusible material are disposed on a shape forming mandrel with seams in the layers that may be configured to produce inflatable channels. The graft section and shape forming mandrel can be placed in a mold which constrains an outer layer or layers of fusible material while the inflatable channels are being expanded and the fusible material of the graft section fixed. In some embodiments, the fusible material of the graft section may be fixed by a sintering process.

RELATED APPLICATIONS

This application is a divisional of U.S. Ser. No. 10/029,570, filed onDec. 20, 2001, now U.S. Pat. No. 6,776,604. Said application Ser. No.10/029,570 is related to U.S. Ser. No. 10/029,584; filed on Dec. 20,2001, entitled “Endovascular Graft And Method For Manufacture”; U.S.Ser. No. 10/029,557; filed Dec. 20, 2001, entitled “Method and Apparatusfor Manufacturing an Endovascular Graft Section”; and U.S. Ser. No.10/029,559, filed on Dec. 20, 2001, entitled “Advanced EndovascularGraft.” All of the above related applications are commonly owned. All ofthe above applications are hereby incorporated by reference, each intheir entirety.

BACKGROUND

Embodiments of the device and method discussed herein relate to a systemand method for manufacturing intracorporeal devices used to replace,strengthen, or bypass body channels or lumens of patients; inparticular, those channels or lumens that have been affected byconditions such as abdominal aortic aneurysms.

Existing methods of treating abdominal aortic aneurysms include invasivesurgical methods with grafts used to replace the diseased portion of theartery. Although improvements in surgical and anesthetic techniques havereduced perioperative and postoperative morbidity and mortality,significant risks associated with surgical repair (including myocardialinfarction and other complications related to coronary artery disease)still remain.

Due to the inherent hazards and complexities of such surgicalprocedures, various attempts have been made to develop alternativerepair methods that involve the endovascular deployment of grafts withinaortic aneurysms. One such method is the non-invasive technique ofpercutaneous delivery of grafts and stent-grafts by a catheter-basedsystem. Such a method is described by Lawrence, Jr. et al. in“Percutaneous Endovascular Graft: Experimental Evaluation”, Radiology(1987). Lawrence et al. describe therein the use of a Gianturco stent asdisclosed in U.S. Pat. No. 4,580,568 to Gianturco. The stent is used toposition a Dacron® fabric graft within the vessel. The Dacron® graft iscompressed within the catheter and then deployed within the vessel to betreated.

A similar procedure is described by Mirich et al. in “PercutaneouslyPlaced Endovascular Grafts for Aortic Aneurysms: Feasibility Study,”Radiology (1989). Mirich et al. describe therein a self-expandingmetallic structure covered by a nylon fabric, the structure beinganchored by barbs at the proximal and distal ends.

An improvement to percutaneously delivered grafts and stent-graftsresults from the use of materials such as expandedpolytetrafluoroethylene (ePTFE) for a graft body. This material, andothers like it, have clinically beneficial properties. However,manufacturing a graft from ePTFE can be difficult and expensive. Forexample, it is difficult to bond ePTFE with conventional methods such asadhesives, etc. In addition, depending on the type of ePTFE, thematerial can exhibit anisotropic behavior. Grafts are generally deployedin arterial systems whose environments are dynamic and which subject thedevices to significant flexing and changing fluid pressure flow.Stresses are generated that are cyclic and potentially destructive tointerface points of grafts, particularly interface between soft andrelatively hard or high strength materials.

What has been needed is a method and device for manufacturingintracorporeal devices used to replace, strengthen or bypass bodychannels or lumens of a patient from ePTFE and similar materials whichis reliable, efficient and cost effective.

SUMMARY

An embodiment of the invention is directed to a mold for manufacture ofan endovascular graft, or section thereof, which has at least oneinflatable channel or cuff. The mold has a plurality of mold bodyportions configured to mate with at least one other-mold body portion toproduce an assembled mold having a main cavity portion. The main cavityportion has an inside surface contour that matches an outside surfacecontour of the graft section with the at least one inflatable channel orcuff in an expanded state. In some embodiments, the main cavity portionmay include channel cavities, cuff cavities, longitudinal channelcavities or helical channel cavities which are configured to correspondto inflatable channels, inflatable cuffs, inflatable longitudinalchannels or inflatable helical channels of the graft when in an expandedstate. In other embodiments, the mold can have a plurality ofcircumferential channel cavities and at least one longitudinal channelcavity or helical channel cavity that transects the circumferentialchannel cavities.

Another embodiment is directed to an outer constraint device in the formof a mold for manufacture of an endovascular graft, or section thereof,which has at least one inflatable channel or cuff. The mold has a firstmold body portion having a main cavity portion with an inside surfacecontour that is configured to correspond to an outside surface contourof the graft section with the at least one inflatable channel or cuff inan expanded state. The mold also has a second mold body portionconfigured to mate with the first mold body portion having a main cavityportion with an inside surface contour that is configured to correspondto an outside surface contour of the graft section with the at least oneinflatable channel or cuff in an expanded state.

A further embodiment of the invention is directed to a pressure line foruse in the manufacture of an endovascular graft, or section thereof. Thepressure line has an elongate conduit with an input end, an output endand a permeable section. The permeable section can have a permeabilitygradient which increases with distance from the input end. In oneembodiment, the permeability of the pressure line increases about 5 toabout 20 percent per centimeter in a direction from the input end to theoutput end along the permeable section. The permeability gradient in thepermeable section can be created by a plurality of outlet orifices inthe elongate conduit which increase in diameter with an increase indistance from input end. In addition, such outlet orifices can be spacedlongitudinally from each other so as to match a longitudinal spacing ofa plurality of circumferential inflatable channels of the endovasculargraft.

Another embodiment of the invention includes a mandrel for shape formingan endovascular graft, or section thereof. The mandrel has a middlesection and a first end section with at least a portion which has alarger outer transverse dimension than an outer transverse dimension ofthe middle section and which is removably secured to a first end of themiddle section. A second end section is disposed at a second end of themiddle section with at least a portion which has a larger outertransverse dimension than an outer transverse dimension of the middlesection. In a particular embodiment, the first end section and secondend section are removably secured to the middle section by threadedportions and a longitudinal axis of the first end section, second endsection and middle section can be substantially coaxial. In anotherembodiment, the middle section can have a pressure line recess in theform of a longitudinal channel in an outer surface of the middle sectionwhich is configured to accept a pressure line.

Embodiments of the invention can include an assembly for manufacture ofan endovascular graft, or section thereof, which has at least oneinflatable cuff or channel on a section thereof. The assembly consistsof a mandrel having an elongate body having an outer surface counterconfigured to support an inside surface of the graft section. The graftsection having at least one inflatable cuff or channel is disposed aboutat least a portion of the mandrel. A pressure line having an elongateconduit with an input end, an output end and a permeability gradientwhich increases with distance from the input end is in fluidcommunication with an inflatable cuff or channel of the graft section. Amold is at least partially disposed about the graft section, thepressure line and the mandrel. The mold has a plurality of mold bodyportions configured to mate together to produce an assembled mold havinga main cavity portion. The main cavity portion has an inside surfacecontour that matches an outside surface contour of the graft sectionwith the at least one inflatable cuff or channel in an expanded state.The inside surface contour is configured to radially constrain an outerlayer or layers of the at least one inflatable cuff or channel duringexpansion of the cuff or channel. In some embodiments, the plurality oforifices of the elongate conduit of the pressure line can besubstantially aligned with circumferential channel cavities of the mold.

Embodiments of the invention which include methods for forming aninflatable channel or cuff of an endovascular graft, or section thereof,will now be described. An graft section is provided with at least oneinflatable channel or cuff formed between layers of graft material ofthe graft section in an unexpanded state. A mold is provided which has amain cavity portion With an inside surface contour that corresponds toan outside surface contour of the graft section with the at least oneinflatable channel or cuff in an expanded state. The graft section isthen positioned in the main cavity portion of the mold with the at leastone inflatable channel or cuff-of the graft section in an unexpandedstate positioned to expand into corresponding channel or cuff cavityportions of the main cavity portion. Once the graft section is properlypositioned within the main cavity portion of the mold, pressurized gasis injected into the at least one inflatable channel or cuff to expandthe at least one inflatable channel or cuff. Thereafter, the graftmaterial of the at least one inflatable channel or cuff is fixed withthe at least one inflatable channel or cuff in an expanded state.

In a particular embodiment of the method, a pressure line having anelongate conduit with a permeable section which includes a permeabilitygradient can be placed in fluid communication with at least oneinflatable channel or cuff of the graft section. Thereafter, pressurizedgas can be injected into the at least one inflatable channel or cuffthrough the permeable section of the pressure line. In addition, anoptional internal radial support can be positioned within the graftsection prior to expansion of the at least one inflatable channel orcuff. The internal radial support may consist of a mandrel which isdisposed within the graft section prior to placing the graft sectioninto the mold so as to radially support the inside surface of the graftsection during injection of the pressurized gas. In one embodiment, thegraft material of the at least one inflatable channel or cuff is fixedby sintering. In another embodiment of a method for forming at least oneinflatable channel or cuff of an endovascular graft, or section thereof,a pressurized liquid can be injected into the inflatable channel or cuffof the graft section. Some expansion of the inflatable channel or cuffcan be carried out by vapor pressure from boiling of pressurized liquidduring fixing of the graft material with the liquid in the inflatablechannel or cuff.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a layer of fusible material being positioned onto ashape forming mandrel.

FIG. 2 shows a first layer of fusible material disposed on a shapeforming mandrel.

FIG. 2A is a transverse cross sectional view of the first layer offusible material and the shape forming mandrel of FIG. 2 taken alonglines 2A—2A in FIG. 2.

FIG. 3 illustrates an additional layer of fusible material beingdeposited onto a shape forming mandrel.

FIG. 4 shows the first layer of fusible material being trimmed by aninstrument.

FIG. 5 is a transverse cross sectional view of the layers of fusiblematerial and shape forming mandrel of FIG. 5 taken along lines 5—5 ofFIG. 4.

FIG. 6 illustrates additional layers of fusible material being depositedon the shape forming mandrel.

FIG. 7 illustrates an inflation line being positioned on the first andadditional layers of fusible material of FIG. 6.

FIGS. 7A and 7B illustrate the formation of the inflation line of FIG.7.

FIG. 8 shows two expandable members positioned on the layers of fusiblematerial of FIG. 7.

FIG. 9 illustrates the deposition of an adhesive or melt processiblematerial adjacent a connector member of the graft body section underconstruction.

FIG. 10 shows another additional layer of fusible material beingdeposited onto the graft body section.

FIG. 11 illustrates excess fusible material being trimmed from the firstend and second end of the graft body- section adjacent the connectormembers.

FIG. 12 is an elevational view of the graft body section with thefusible material trimmed away and removed.

FIG. 13A is a side view from the right hand side of a five axis seamforming apparatus.

FIG. 13B is a side view from the left hand side of a five axis seamforming apparatus.

FIG. 13C is a front view of the five axis seam forming apparatus ofFIGS. 13A and 13B.

FIG. 13D shows a stylus tip in contact with a transverse cross sectionedview of a cylindrical shape forming member with an axis of the stylustip oriented at an angle with the tangent of the shape forming member atthe point of contact therebetween.

FIG. 13E illustrates a stylus tip in contact with a plurality of layersof fusible material in a substantially flat configuration with thelongitudinal axis of the stylus tip at an angle with respect to a linewhich is orthogonal to the surface of the layers.

FIG. 13F is a front view of the seam forming apparatus with a shapeforming mandrel and a graft body section on the shape forming mandrelpositioned in the chuck of the seam forming member mount system.

FIG. 13G illustrates a distal extremity or tip of a stylus in contactwith the layers of fusible material of the graft body section.

FIG. 13H illustrates the tip of a stylus in contact with layers offusible material of the graft body section, forming a seam in thelayers.

FIG. 14 shows inflation channels being formed in the layers of fusiblematerial on the shape forming mandrel by the seam forming apparatusstylus tip.

FIG. 15 shows the graft body section with the channel formation completeand pressurized fluid being injected into an inflatable channel networkin order to expand the inflatable channels.

FIG. 16A illustrates one half of an embodiment of a two-piece mold foruse during expansion of the inflatable channels formed by the seamforming apparatus. FIG. 16B is an end view showing the shape formingmandrel and graft body section within both halves of the mold.

FIG. 16C shows the graft body section and shape forming mandrel disposedwithin the mold cavity (with one half of the mold removed for clarity ofillustration) with a fluid being injected into the inflatable channelsof the graft body section in order to keep the inflatable channels in anexpanded state during the fixing or sintering of the fusible material.

FIG. 17 illustrates an outer layer or layers of fusible material beingforced into the mold cavity of a portion of the mold by pressurizedfluid as indicated by the dotted line.

FIG. 18 is an elevational view in partial section of an embodiment of aninflatable endovascular graft of the present invention.

FIG. 19 is an enlarged view of the graft of FIG. 18 taken at the dashedcircle indicated by numeral 19 in FIG. 18.

FIG. 20 is an enlarged view in section- taken along lines 20—20 in FIG.18.

FIG. 21 is a transverse cross sectional view of the graft of FIG. 18taken along lines 21—21 in FIG. 18.

FIG. 22 is a transverse cross sectional view of the graft of FIG. 18taken along lines 22—22 in FIG. 18.

FIG. 23 is a transverse cross sectional view of the graft of FIG. 18taken along lines 23—23 in FIG. 18.

FIG. 24 is an elevational view of an embodiment of a shape formingmandrel with a pressure line recess.

FIG. 25 is a transverse cross sectional view of the shape formingmandrel of FIG. 24 taken at lines 25—25.

FIG. 26 is a transverse cross sectional view of the shape formingmandrel of FIG. 24 taken at lines 26—26.

FIG. 27 shows an end view of a mold body portion. FIG. 28 shows a sideview of a longitudinal section of a mold body portion.

FIG. 29 is a perspective view of a mold body portion separated fromanother mold body portion.

FIG. 30 shows an elevational view of a pressure line having features ofthe invention.

FIG. 31 is a transverse cross sectional view of the pressure line ofFIG. 30 taken at lines 31—31.

FIG. 32 is a transverse cross sectional view of the pressure line ofFIG. 30 taken at lines 32—32, which shows a D-shaped configuration of aportion of the pressure line.

FIG. 33 is a transverse cross sectional view of the pressure line withexit ports of FIG. 30 taken at lines 33—33.

FIG. 34 shows a graft section and shape forming mandrel disposed withina mold cavity portion with one of the mold body portions not shown forclarity of illustration.

FIG. 35 is a transverse cross sectional view of the graft section,mandrel for shape forming the endovascular graft, and the pressure lineembedded within the layers of the fusible material taken at lines 35—35of FIG. 34.

FIG. 36 is an enlarged view showing the pressure line within the layersof fusible material at encircled area 36 of FIG. 35.

FIG. 37 is a top partial cutaway view of the graft section land shapeforming mandrel disposed within a mold cavity portion, with one of themold body portions not shown for clarity of illustration, showing thepressure line disposed within a longitudinal channel of the graft and agas being injected into the pressure line of the graft section,expanding the inflatable channels and cuffs.

FIG. 38 is a top partial cutaway view of the graft section and shapeforming mandrel disposed within a mold cavity portion, with one of themold body portions not shown for clarity of illustration, showing thepressure line disposed within a longitudinal channel and with theinflatable channels and cuffs in an expanded state.

FIG. 39 is a top partial cutaway view of an alternate embodiment of agraft section and shape forming mandrel disposed within a mold cavityportion, with one of the mold body portions not shown for clarity ofillustration, showing the pressure line disposed within a temporaryexpansion channel that is in fluid communication with an expandedhelical inflatable channel.

FIG. 40 shows the graft section of FIG. 39 with the temporary expansionchannel sealed.

FIG. 41 is a top partial cutaway view of an alternate embodiment of agraft section and shape forming mandrel disposed within a mold cavityportion, with one of the mold body portions not shown for clarity ofillustration, with a pressure line disposed within a temporary expansionchannel.

FIG. 42 shows the graft section of FIG. 41 with the temporary expansionchannel sealed in selected portions.

DETAILED DESCRIPTION

FIG. 1 illustrates a sheet of fusible material 10 stored on an elongatedrum 11. The drum 11 is rotatable, substantially circular in transversecross section and has a transverse dimension in the longitudinal center12 that is greater than the transverse dimension of either end of thedrum. The sheet of fusible material 10 is being rolled from the elongatedrum in a single layer 13 onto an interior surface support means in theform of a cylindrical or tapered (conical) shape forming member ormandrel 14 to form a body section 15 of an endovascular graft 16. Thebody section 15 has a proximal end 17 and a distal end 18. For thepurposes of this application, with reference to endovascular graftdevices, the proximal end 17 describes the end of the graft that will beoriented towards the oncoming flow of bodily fluid, usually blood, whenthe device is deployed within a conduit of a patient's body. The distalend 18 of the graft is the end opposite the proximal end.

A single layer of fusible material 13 is a term that generally refers toa sheet of material that is not easily separated by mechanicalmanipulation into additional layers. The shape forming mandrel 14 issubstantially cylindrical in configuration, although otherconfigurations are possible. Middle section 20 of mandrel 14 shown inFIGS. 1–2 has a transverse dimension which is smaller than thetransverse dimension of a first end section 21 and a second end section22. The shape forming mandrel may have a first tapered section 23 at thefirst end and a second tapered section 24 at the second end. The sheetof fusible material 10 is shown being rolled off the elongate drum 11 inthe direction indicated by the arrow 11A with the lead end 25 of thefirst layer of fusible material 10 oriented longitudinally along anoutside surface 14A of the shape forming mandrel 14.

The fusible material in the embodiment illustrated in FIG. 1 is ePTFEthat ranges from about 0.0005 to about 0.010 inch in thickness;specifically from about 0.001 to about 0.003 inch in thickness. Thesheet being disposed or rolled onto the shape forming mandrel 14 mayrange from about 2 to about 10 inches in width; specifically, from about3 to about 7 inches in width, depending on the indication and size ofthe end product.

The ePTFE material sheet 10 in FIG. 1 is a fluoropolymer with a node andfibril composition with the fibrils oriented in primarily a uniaxialdirection substantially aligned with the longitudinal axis of shapeforming mandrel 14. Other nodal/fibril orientations of ePTFE could alsobe used for this layer, including multiaxially oriented fibrilconfigurations or uniaxial material oriented substantiallycircumferentially about shape forming mandrel 14 or at any desired anglebetween substantial alignment with the longitudinal axis and substantialalignment with a circumferential line about the shape forming mandrel14. Uniaxially oriented ePTFE materials tend to have greater tensilestrength along the direction of fibril orientation, so fibrilorientation can be chosen to accommodate the greatest stresses imposedupon the finished product for the particular layer, combination oflayers, and portion of the product where such stress accommodation isneeded.

The layers of fusible material made of ePTFE are generally applied orwrapped in an unsintered state. By applying the ePTFE layers in anunsintered or partially sintered state, the graft body section 15, uponcompletion, can then be sintered or fixed as a whole in order to form acohesive monolithic structure with all contacting surfaces of ePTFElayers achieving some level of interlayer adhesion. It may, however, bedesirable to apply some layers of fusible material that have beenpre-sintered or pre-fixed in order to achieve a desired result or toassist in the handling of the materials during the construction process.For example, it may be desirable in some embodiments to sinter thesingle layer 13 of fusible material applied to the shape forming mandrel14 in order to act as a better insulator between the shape formingmandrel 14, which can act as a significant heat sink, and subsequentlayers of fusible material which may be welded by seam formation in somelocations in order to create inflatable channels.

The amount of expansion of the ePTFE material used for the constructionof endovascular grafts and other devices can vary significantlydepending on the desired characteristics of the material and thefinished product. Typically, the ePTFE materials processed by thedevices and methods discussed herein may have a density ranging fromabout 0.4 to about 2 grams/cc; specifically, from about 0.5 to about 0.9grams/cc. The nodal spacing of the uniaxial ePTFE material may rangefrom about 0.5 to about 200 microns; specifically, from about 5 to about35 microns. The nodal spacing for multiaxial EPTFE material may rangefrom about 0.5 to about 20 microns; specifically, from about 1 to about2 microns.

Although FIG. 1 illustrates a layer of fusible material that is made ofePTFE, the methods described herein are also suitable for a variety ofother fusible materials. Examples of other suitable fusible materialsfor endovascular graft construction and other applications include PTFE,porous PTFE, ultra high molecular weight polyethylene, polyesters, andthe like.

FIGS. 2 and 2A depict a first layer of fusible material 26 disposed onthe shape forming mandrel 14 with an overlapped portion 27 of the firstlayer 26 on itself. A terminal end 28 of the first layer 26 is seenextending longitudinally along the length of the shape forming mandrel14. As the layer of fusible material is wrapped onto shape formingmandrel 14, some tension may be provided on the sheet of material by theelongate drum 11. As a result of this tension and the flexible andconforming properties of the ePTFE material, the first layer of material26 conforms closely to the outer contour of the shape forming mandrel 14as is illustrated in FIG. 2.

In some embodiments, it may be desirable to pass the tip of a seamforming tool or similar device (not shown) along the overlapped portion27 of first layer 26 in a longitudinal direction in order to form a seam(not shown) along the overlapped portion 27 of first layer 26. A toolsuitable for forming such a longitudinal seam is a soldering iron with asmooth, rounded tip that will not catch or tear the layer of fusiblematerial. An appropriate operating temperature for the tip of such atool may range from about 320 to about 550 degrees Celsius;specifically, from about 380 to about 420 degrees Celsius.

FIG. 3 illustrates an additional layer of fusible material 30 beingdisposed or wrapped onto the first layer of fusible material 26 in amanner similar to that described above for the first layer 26. Bothuniaxial and multiaxial ePTFE may be used for this additional layer 30.A lead end 31 of the additional layer can be seen adjacent the terminalend 28 of the first layer 26. Tension on the additional layer of fusiblematerial 30 helps to make the additional layer 30 conform to the shapeforming mandrel 14 as seen in the illustration. Although a singleadditional layer 30 is shown in FIG. 3 as being disposed onto the firstlayer 26, it is within the scope of the invention to wrap multipleadditional layers 30 of fusible material in this step. We have foundthat wrapping two additional layers 30 of multiaxial ePTFE onto thefirst layer 26 helps to form a useful graft body section 15.

FIG. 4 shows an optional step in which the first and additional layersof fusible material 26 and 30 which form the graft body section 15 underconstruction are trimmed by knife edge 32 or a similar tool which ispressed against the layers of material and moved circumferentially aboutthe shape forming mandrel 14. FIG. 5 is a transverse cross sectionalview of the shape forming mandrel 14 and graft body section 15 of FIG. 5taken along lines 5—5 in FIG. 4. The overlapped portion 27 of the firstlayer 26 and an overlapped portion 33 of the additional layer 30 offusible material can be seen. It may be desirable to create alongitudinal seam in the overlapped portion 33 of the additional layer30 in a manner similar to that of the first layer 26 discussed aboveusing the same or similar tools.

FIG. 6 illustrates a proximal end wrap 34 of fusible material beingapplied to the additional layer 30 of graft body section 15, preferablyunder some tension. We have found it useful to have end wrap 34 beuniaxial ePTFE, with the fibrils of the end wrap material orientedcircumferentially about the shape forming mandrel 14, although otherorientations and types of ePTFE are possible. The end wrap material mayhave a thickness ranging from about 0.0005 to about 0.005 inch;specifically, from about 0.001 to about 0.002 inch. The width of the endwrap material may range from about 0.25 to about 2.0 inch; specifically,from about 0.5 to about 1.0 inch. One or more layers of end wrap 34 (inany desired orientation) may be built up onto the proximal end 17 ofgraft body section 15 on shape forming mandrel 14. The additional endwrap layer or layers 34 may be applied in a manner similar to that ofthe first layer 26 and additional layers 30 as discussed above.

FIG. 7 shows graft body section 15 with the end wrap layer 34 completedwith an inflation line 36 disposed on or near the distal end. 18 ofgraft body section 15. The inflation line 36 may be constructed as shownin FIGS. 7A and 7B of ePTFE by wrapping one or more layers of thematerial about a cylindrical mandrel 37. A longitudinal seam 38 can thenbe formed in an overlapped portion of the layers by passing the tip of aseam forming tool 39 along the overlapped portion of the first layer ina longitudinal direction in order to form a seam 38 along the overlappedportion of the layers of the inflation line 36. A tool suitable forforming such a longitudinal seam is a soldering iron with a smoothrounded tip that will not catch or tear the layer of fusible material;operating temperatures for the tip may range as previously discussed.Alternatively, the inflation line 36 may be formed using an ePTFEextrusion placed over a mandrel.

Once seam 38 is formed in inflation line 36, the fusible material ofinflation line 36 may can be fixed or sintered by heating to apredetermined temperature for a predetermined time. For embodiments ofthe inflation line 36 made of ePTFE, the layers are sintered by bringingthe layered assembly to a temperature ranging from about 335 to about380 degrees Celsius (for unsintered material) and about 320 to about 380degrees Celsius (for sintering material that was previously sintered)and then cooling the assembly to a temperature ranging from about 180 toabout 220 degrees Celsius. The inflation line 36 may then be removedfrom mandrel 37 and disposed on a graft body assembly 40 as shown inFIG. 7. The inflation line 36 may be pre-fixed or pre-sintered to avoidhaving the inner surfaces of the inflation line 36 stick together duringthe construction and processing of the graft and possibly, block theinflation line 36.

In FIG. 8, expandable members in the form of a proximal connector member41 and a distal connector member 42 have been disposed onto the graftbody section 15 towards the respective graft body section proximal end17 and distal end 18. The proximal connector member 41 is an elongateflexible metal element configured as a ring, with the ring having azig-zag or serpentine pattern around the circumference of the ring. Thedistal connector member 42 can have a similar configuration; note thefeature of this element in which an extended apex 44 is disposed overinflation line 36 to further stabilize graft section 15. Thisconfiguration allows the connector members 41 and 42 to be radiallyconstrained and radially expanded while maintaining a circular ringconfiguration. The embodiment of the connector members 41 and 42 shownin FIG. 8 may be constructed of any suitable biocompatible material;most suitable are metals, alloys, polymers and their composites known tohave superelastic properties that allow for high levels of strainwithout plastic deformation, such as nickel titanium (NiTi). Otheralloys such as stainless steel may also be used. Connector members 41and 42 shown are also configured to be self-expanding from a radiallyconstrained state. The serpentine pattern of the connector members 41and 42 is disposed over base layers of the graft body section as areconnector elements 43 which are disposed on certain apices 44 of theserpentine pattern of the connector members 41 and 42. The embodimentsof the connector members 41 and 42 shown in FIG. 8 have been shapeformed to lie substantially flat against the contour of the outersurface of the shape forming mandrel 14. Although the embodiment of FIG.8 illustrates connector members 41 and 42 being disposed upon the graftbody section 15, expandable members including stents or the like may beused in place of the connector members 41 and 42.

An optional adhesive or melt-processible material such as FEP or PFA maybe deposited adjacent the connector members 41 and 42 prior to theaddition of additional layers of fusible material to the graft bodysection 15, as is shown in FIG. 9. Materials such as FEP or PFA can helpthe layers of fusible material to adhere to the connector members 41 and42, to inflation line 36 (in the case of distal member 42), and to eachother. In addition, such material may serve to provide strain reliefbetween connector members 41 and 42 and the adhered or bonded layers offusible material (and inflation line 36) adjacent the wire of theconnector members 41 and 42. It has been determined that one of theareas of greatest concentrated stress within an endovascular structuresuch as that described herein, when deployed within a dynamic biologicalsystem, such as an artery of a human patient, is at the junction betweenthe connector members 41 and 42 and graft body section 15. Therefore, itmay be desirable to include materials such as FEP or PFA or some otherform of strength enhancement or strain relief in the vicinity of thisjunction.

An outer overall wrap layer 50 may thereafter be applied to the graftbody section 15 and connector members 41 and 42 as shown in FIG. 10. Theouter overall wrap layer 50 can include one, two, three or more layersof multiaxial ePTFE, usually about 2 to about 4 layers, but uniaxialePTFE other suitable fusible materials, fibril orientation and layernumbers could also be. used. The outer overall wrap layer 50 is mostusefully applied under some tension in order for the layer or layers tobest conform to the outer contour of the shape forming mandrel 14 andgraft body section 15. When the outer layer 50 comprises multiaxialePTFE, there is generally no substantially preferred orientation ofnodes and fibrils within the microstructure of the material. This resultin a generally isotropic material whose mechanical properties, such astensile strength, are generally comparable in all directions (as opposedto significantly different properties in different directions foruniaxially expanded ePTFE). The density and thickness of the multiaxialmaterial can be the same as or similar to those dimensions discussedabove.

Although not shown in the figures, we have found it useful to add one ormore optional cuff-reinforcing layers prior to the addition of anoverall wrap layer 50 as discussed below in conjunction with FIG. 10.Typically this cuff-reinforcing layer is circumferentially applied tograft body section 15 at or near the graft body section proximal end 17so to provide additional strength to the graft body section proximal end17 in those designs in which a proximal cuff (and possibly a proximalrib) are used. Typically the graft experiences-larger strains duringfabrication and in service in the region of the proximal cuff,especially if a larger cuff is present. This optional cuff-reinforcinglayer typically is multiaxial ePTFE, although uniaxial ePTFE and othermaterials may be used as well. We have found effective acuff-reinforcing layer width from about 20 to about 100 mm;specifically, about 70 mm. Functionally, however, any width sufficientto reinforce the proximal end of graft body section 15 may be used.

Once the additional layer or layers of fusible material and additionalgraft elements such as the connector members 41 and 42 and inflationline 36 have been applied, any excess fusible material may be trimmedaway from the proximal end 17 and distal end 18 of graft body section15. FIG. 11 illustrates one or more layers of fusible material beingtrimmed from the proximal end 17 and distal end 18 of the graft bodysection 15 so as to leave the connector members 41 and 42 embeddedbetween layers of fusible material but with the connector elements 43exposed and a distal end 51 of the inflation line 36 exposed as shown inFIG. 12. Once the fusible material has been trimmed from the proximalend 17 and the distal end 18, as discussed above, an additional processmay optionally be performed on the proximal end 17, distal end 18 orboth the proximal end and distal end 17 and 18. In this optional process(not shown in the figures), the outer wrap 50 is removed from a portionof the connector members 41 and 42 so as to expose a portion of theconnector members 41 and 42 and the additional layer of fusible material30 beneath the connector member 42 and the proximal end wrap 34 beneathconnector member 41. Once exposed, one or more layers of the additionallayer or layers 30 or proximal end wrap 34 may have cuts made therein toform flaps which can be folded back over the respective connectormembers 42 and 41 and secured to form a joint (not shown). One or morelayers of fusible material can then be disposed over such a joint toprovide additional strength and cover up the joint. The construction ofsuch a joint is discussed in copending U.S. patent application“Endovascular Graft Joint and Method for Manufacture” by Chobotov et al.which has been incorporated by reference herein.

Once the graft body section 15 has been trimmed, the entire shapeforming mandrel 14 and graft body section 15 assembly is moved to a seamforming apparatus 52 illustrated in FIGS. 13A–13H. This seam formingapparatus 52 has a base 53 and a vertical support platform 54 whichextends vertically upward from the back edge of the base 53. A mountsystem 55 is secured to the base 53 and for the embodiment shown in thefigures, consists of a motor drive chuck unit 56 secured to a riser 57and a live center unit 58 secured to a riser 59. Both risers 57 and 59are secured to the base 53 as shown. The axis of rotation 55A of thechuck 60 of the motor drive chuck unit 56 and the axis of rotation 55Bof the live center 61 of the live center unit 58 are aligned orconcentric as indicated by dashed line 55C. A motor is mechanicallycoupled to the chuck 60 of the motor drive chuck unit 56 and serves torotate the chuck 60 in a controllable manner.

A vertical translation rack 62 is secured to the vertical supportplatform 54 and extends from the base 53 to the top of the verticalsupport platform 54. A vertical car 63 is slidingly engaged on thevertical translation rack 62 and can be moved along the verticaltranslation rack 62, as shown by arrows 63A, in a controllable manner bya motor and pinion assembly (not shown) secured to the vertical car 63.A horizontal translation rack 64 is secured to the vertical car 63 andextends from the left side of the vertical car 63 to the right side ofthe vertical car 63. A horizontal car 65 is slidingly engaged on thehorizontal translation rack 64 and can be moved along the horizontalrack 64, as shown by arrow 64A, in a controllable manner by a motor andpinion assembly (not shown) which is secured to the horizontal car 65.

A stylus rotation unit 66 is slidingly engaged with a second horizontaltranslation rack 65A disposed on the horizontal car 65 and can be movedtowards and away from the vertical car 63 and vertical support platform54 in a controllable manner as shown by arrow 66A. A stylus rotationshaft 67 extends vertically downward from the stylus rotation unit 66and rotates about an axis as indicated by dashed line 67B and arrow 67Ain a controllable manner. A stylus mount 68 is secured to the bottom endof the rotation shaft 67 and has a main body portion 69 and a styluspivot shaft 70. A stylus housing 71 is rotatably secured to the stylusmount 68 by the stylus pivot shaft 70. A torsion spring 72 is disposedbetween the proximal end of the stylus housing 73 and the stylus mount68 and applies a predetermined amount of compressive, or spring-loadedforce to the proximal end 73 of the stylus housing 71. This in turndetermines the amount of tip pressure applied by a distal extremity 80of a stylus tip 75 disposed at the distal end section 78 of the stylus79 (which is in turn secured to the distal end section 76 of the stylushousing 71).

The base 53 of seam forming apparatus 52 is secured to a control unithousing 77 which contains one or more power supplies, a CPU, and amemory storage unit that are used in an automated fashion to controlmovement between the graft body 15 section and the stylus tip 75 in thevarious degrees of freedom therebetween. The embodiment of the seamforming apparatus 52 described above has five axes of movement (ordegrees of freedom) between an object secured to the chuck 60 and livecenter, 61 and the stylus tip 75; however, it is possible to haveadditional axes of movement, such as six, seven, or more. Also, for someconfigurations and seam forming processes, it may be possible to usefewer axes of movement, such as two, three, or four. In addition, anynumber of configurations may be used to achieve the desired number ofdegrees of freedom between the stylus 79 and the mounted device. Forexample, additional axes of translation-or rotation could be added tothe mount system and taken away from the stylus rotation unit 66.Although the embodiment of the shape forming mandrel 14 shown in FIGS.1–17 is cylindrical, a five axis or six axis seam forming apparatus hasthe capability and versatility to accurately create seams of most anydesired configuration on a shape forming member or mandrel of a widevariety of shapes and sizes. For example, a “Y” shaped mandrel suitablefor generating a bifurcated graft body section could be navigated, bythe five axis seam forming apparatus illustrated herein, as well asother shapes. Finally, seam forming apparatus 52 illustrated herein isbut one of a number of devices and configurations capable of achievingthe seams of the present inventions.

FIG. 13D illustrates an enlarged view of a stylus tip 75 applied to arotating cylindrical surface 86B with the surface rotating in acounterclockwise direction as indicated by arrow 86A. The cylindricalsurface can support one or more layers of fusible material (not shown)between the distal extremity 80 of the stylus tip 75 and the surface 86Bwhich require seam to be formed therein. The stylus tip 75 has alongitudinal axis that forms an angle 86 with a tangent to the surfaceof the cylindrical surface indicated by dashed line 87. Although notnecessary, we have found it useful to have the object in contact withthe stylus tip 75 rotating or moving in a direction as show in FIG. 13D,relative to angle 86 in order to prevent chatter of the configuration ordistortion of fusible material on the surface 86A. In one embodiment,angle 86 may range from about 5 to about 60 degrees; specifically, fromabout 10 to about 20 degrees. It is also useful if the distal extremity80 of the stylus tip 75 has a smooth surface and is radiused. A suitableradius for one embodiment may range from about 0.01 to about 0.030 inch;specifically, from about 0.015 to about 0.02 inch.

FIG. 13E shows a similar relationship between a stylus tip 75 and hardsurface 81. Surface 81 may have one or more layers of fusible material(not shown) disposed thereon between distal extremity 80 and surface 81.A longitudinal axis 75A of stylus tip 75 forms an angle 86 with thedashed line 89 that is parallel to surface 81. Angle 88 in thisembodiment should range from about 5 to about 60 degrees; specifically,from about 10 to about 20 degrees, so to ensure smooth relative motionbetween surface 81 and tip 75. The surface 81 is shown moving relativeto the stylus tip 75 in the direction indicated by arrow 81A.

The pressure exerted by the extremity 80 of stylus tip 75 on thematerial being processed is another parameter that can affect thequality of a seam formed in layers of fusible material. In oneembodiment in which the stylus tip is heated, the pressure exerted bythe distal extremity 80 of the stylus tip 75 may range from about 100 toabout 6,000 pounds per square inch (psi); specifically, from about 300to about 3,000 psi. The speed of the heated stylus 75 relative to thematerial being processed, such as that of graft body section 15, mayrange from about 0.2 to about 10 mm per second, specifically, from about0.5 to about 1.5 mm per second. The temperature of the distal extremity80 of the heated stylus tip 75 in this embodiment may range from about320 to about 550 degrees Celsius; specifically, about 380 to about 420degrees Celsius.

Seam formation for ePTFE normally occurs by virtue of the application ofboth heat and pressure. The temperatures at the tip of the heated stylus75 during such seam formation are generally above the melting point ofhighly crystalline ePTFE, which may range be from about 327 to about 340degrees Celsius, depending in part on whether the material is virginmaterial or has previously been sintered). In one embodiment, the stylustip temperature for ePTFE welding and seam formation is about 400degrees Celsius. Pressing such a heated tip 75 into the layers of ePTFEagainst a hard surface such as the outside surface of the shape formingmandrel) compacts and heats the adjacent layers to form a seam withadhesion between at least two of, if not all, the layers. At the seamlocation and perhaps some distance away from the seam, the ePTFEgenerally transforms from an expanded state with a low specific gravityto a non-expanded state (i.e., PTFE) with a relatively high specificgravity. Some meshing and entanglement of nodes and fibrils of adjacentlayers of ePTFE may occur and add to the strength of the seam formed bythermal-compaction. The overall result of a well-formed seam between twoor more layers of ePTFE is adhesion that can be nearly as strong or asstrong as the material adjacent the seam. The microstructure of thelayers may change in the seam vicinity such that the seam will beimpervious to fluid penetration.

It is important to note that a large number of parameters determine theproper conditions for creating the fusible material seam, especiallywhen that material is ePTFE. Such parameters include, but are notlimited to, the time the stylus tip 75 is in contact with the material(or for continuous seams, the rate of tip movement), the temperature (ofthe tip extremity 80 as well as that of the material, the underlyingsurface 81, and the room), tip contact pressure, the heat capacity ofthe material, the mandrel, and the other equipment, the characteristicsof the material (e.g. the node and fibril spacing, etc.), the number ofmaterial layers present, the contact angle between the tip extremity 80and the material, the shape of the extremity 80, etc. Knowledge of thesevarious parameters is useful in determining the optimal combination ofcontrollable parameters in forming the optimal seam. And althoughtypically a combination of heat and pressure is useful in forming anePTFE seam, under proper conditions a useful seam may be formed bypressure at ambient temperature (followed by elevation to sinteringtemperature); likewise, a useful seam may also be formed by elevatedtemperature and little-to-no applied pressure.

For example, we have created seams in ePTFE that formed an intact,inflatable cuff by the use of a clamshell mold that presented aninterference fit on either side of a cuff zone for the ePTFE. Theapplication of pressure alone without using an elevated temperatureprior to sintering formed a seam sufficient to create a working cuff.

FIG. 13F depicts a front view of the seam forming apparatus 52 with ashape forming mandrel 14 secured to the chuck 60 and the live centerunit 58. The distal extremity of the heated stylus tip 75 is in contactwith the graft body section 15 which is disposed on the shape formingmandrel 14. The chuck 60 is turning the shape forming mandrel 14 andgraft body section 15 in the direction indicated by the arrow 60A toform a seam 81 between the layers of fusible material of the graft bodysection 15.

FIGS. 13G and 13H illustrate an enlarged view of the heated stylus tip75 in contact with the graft body section 15 in the process of creatingone ore more seams 81 which are configured to form elongate inflatablechannels 82 in the graft body section 15. The term “inflatable channels”may generally be described herein as a substantially enclosed orenclosed volume between layers of fusible material on a graft or graftsection, and in some embodiments, in fluid communication with at leastone inlet port for injection of inflation material. The enclosed volumeof an inflatable channel or cuff may be zero if the inflatable cuff orchannel is collapsed in a non-expanded state. The enclosed volume of aninflatable channel may or may not be collapsible during compression orcompacting of the graft body section 15.

FIG. 13H is an enlarged view in section of the distal extremity 80 ofthe heated stylus tip 75 in contact with layers of fusible material ofgraft body section 15. The layers of fusible material are being heatedand compressed to form a bond 15A therebetween. The seam formingapparatus can position the distal extremity 80 at any desired locationon the graft body section 15 by activation of one or more of the fivemotors controlled by the components in the control unit housing 77. Eachof the five motors controls relative movement between graft body section15 and distal extremity 80 in one degree of freedom. Thus, the distalextremity 80 may be positioned above the surface of the graft bodysection 15, as shown in FIG. 13C, and brought to an appropriatetemperature for seam formation, as discussed above, by resistive heatingor any other appropriate method. Once extremity 80 has reached thetarget temperature, it can be lowered by activation of the motor whichcontrols movement of the vertical car. The extremity 80 can be loweredand horizontally positioned by other control motors until it contactsthe graft body section in a desired predetermined position on graft bodysection 15, as shown in FIG. 13F.

Once distal extremity 80 makes contact with graft body section 15 withthe proper amount of pressure, it begins to form a seam between thelayers of the fusible material of the graft body section as shown inFIG. 13H. The pressure or force exerted by the extremity 80 on the graftbody section may be determined by the spring constant and amount ofdeflection of torsion spring 72 shown in FIGS. 13A and 13B; generally,we have found a force at the extremity 80 ranging from about 0.2 toabout 100 grams to be useful. As the seam formation process continues,the surface of graft body section 15 may be translated with respect tothe distal extremity 80 while desirably maintaining a fixed,predetermined amount of pressure between the distal extremity 80 and thelayers of fusible material of the graft body section. The CPU (or anequivalent device capable of controlling the components of apparatus 52)of the control unit housing 77 may be programmed, for instance, amathematical representation of the outer surface contour of any knownshape forming member or mandrel.

The CPU is thereby able to control movement of the five motors ofapparatus 52, so that distal extremity 80 may follow the contour of theshape forming member while desirably exerting a fixed predeterminedamount of pressure the layers of fusible material disposed between thedistal extremity 80 and the shape forming member. While seam formationis taking place, the pressure exerted by the distal extremity 80 on theshape forming member may be adjusted dynamically. The extremity 80 mayalso be lifted off the graft body section and shape forming member inlocations where there is a break in the desired seam pattern. Oncedistal extremity 80 is positioned above the location of the startingpoint of the next seam following the break, the extremity 80 may then belowered to contact the layers of fusible material, reinitiating the seamformation process.

Use of the seam forming apparatus 52 as described herein is but one of anumber of ways to create the desired seams in the graft body section 15of the present invention. Any suitable process and apparatus may be usedas necessary and the invention is not so limited. For instance, seamsmay also be formed in a graft body section 15 by the use of a fully orpartially heated clamshell mold whose inner surfaces contain raisedseam-forming extensions. These extensions may be configured andpreferentially or generally heated so that when the mold halves areclosed over a graft body section 15 disposed on a mandrel, theextensions apply heat and pressure to the graft body section directlyunder the extensions, thereby “branding” a seam in the graft bodysection in any pattern desired and in a single step, saving much timeover the technique described above in conjunction with seam formingapparatus 52.

If the fusible material comprises ePTFE, it is also possible to infuseor wick an adhesive (such as FEP or PFA) or other material into theePTFE layers such that the material flows into the fibril/node structureof the ePTFE and occupies the pores thereof. Curing or drying thisadhesive material will mechanically lock the ePTFE layers togetherthrough a continuous or semi-continuous network of adhesive material nowpresent in and between the ePTFE layers, effectively bonding the layerstogether.

FIG. 14 illustrates a substantially completed set of seams 81 formed inthe layers of fusible material of the graft body section 15, which seamsform inflatable channels 82. FIG. 15 illustrates graft body section 15as fluid (such as compressed gas) is injected into the inflation line 36and in turn into the inflatable channel network 84 of body section 15,as shown by arrow 84A. The fluid is injected to pre-stress theinflatable channels 82 of body section 15 and expand them outwardradially. The fluid may be delivered or injected through an optionalelongate gas containment means having means for producing a permeabilitygradient in the form of a manifold or pressure line 85. The pressureline 85 shown in FIG. 15 has a configuration with an input (not shown)located outside the inflation line and a plurality of outlet aperturesor orifices (not shown) that may be configured to provide an evendistribution of pressure within the inflatable channel network 84. Otherfluid injection schemes and configurations are of course possible.

Because ePTFE is a porous or semi-permeable material, the pressure ofexerted by injected fluids such as pressurized gas tends to drop off ordiminish with increasing distance away from the outlet apertures ororifices (not shown) of manifold or pressure line 85. Therefore, in someembodiments, pressure line 85 may comprise apertures or orifices (notshown) which, when disposed in graft body section 15, progressivelyincreases in size as one moves distally along the pressure line towardsthe proximal end 17 graft body section 15 in order to compensate for adrop in pressure both within the inflatable channel network 84 andwithin the manifold or pressure line 85 itself.

Once some or all of the inflatable channels 82 have been pre-expanded orpre-stressed, the graft body section 15 and shape forming mandrelassembly 89 may then be positioned within an outer constraint means inthe form of a mold to facilitate the inflatable channel expansion andsintering process. One half of a mold 90 suitable for forming anembodiment of a graft body section 15 such as that shown in FIG. 15 isillustrated in FIG. 16A. A mold half body portion 91 is one of twopieces of mold 90. A mold similar to mold 90 could be made from anynumber of mold body portions configured to fit together. For example, amold 90 could be designed from three, four, five or more mold bodyportions configured to fit together to form a suitable main cavityportion 93 for maintaining the shape of graft body section 15 duringchannel expansion and sintering. For certain configurations, a one piecemold may be used.

Mold body portion 91 has a contact surface 92 and a main cavity portion93. Main cavity portion 93 has an inside surface contour configured tomatch an outside surface contour of the graft body section with theinflatable channels in an expanded state. Optional exhaust channels 92Amay be formed in contact surface 92 and provide an escape flow path forpressurized gas injected into the inflatable channel network 84 duringexpansion of the inflatable channels 82.

The main cavity portion 93 of the FIGS. 16A–16B embodiment issubstantially in the shape of a half cylinder with circumferentialchannel cavities 94 for forming the various inflatable channels 82 ofgraft body section 15. Cavity 93 has a first tapered portion 95 at theproximal end 96 of mold 90. and a second tapered portion 97 at the molddistal end 98. FIG. 16B shows an end view of mold 90 with the two moldbody portions 91 and 100 pressed together with the assembly of the graftbody section 15 and shape forming mandrel 14 disposed mold cavity 93.

FIG. 16C shows the assembly of the graft body section 15 and shapeforming mandrel 14 disposed within mold 90, with the circumferentialinflatable channels 82 of the graft body section 15 aligned with thecircumferential channel cavities 94 of the main cavity portion 93. Onemold body portion 100 of mold 90 is not shown for the purpose of clarityof illustration. A pressurized fluid indicated as being delivered orinjected into manifold or pressure line 85 by arrow 85A.

FIG. 17 illustrates by the phantom lines how the outer layers 94A ofcircumferential inflatable channel 82 of the fusible material of a graftbody section 15 are expanded into the circumferential channel cavity 94of mold cavity 93. The direction of the expansion of the outer layers94A to the position indicated by the phantom lines is indicated by arrow94B. A cross sectional view of the seams 83 of the circumferentialinflatable channel 82 is shown in FIG. 17 as well.

While the graft body section network of inflatable channels 84 is in anexpanded state by virtue of pressurized material being delivered orinjected into pressure line 85, the entire assembly may be positionedwithin an oven or other heating device (not shown) in order to bring thefusible material of graft body section 15 to a suitable temperature foran appropriate amount of time in order to fix or sinter the fusiblematerial. In one embodiment, the fusible material is ePTFE and thesintering process is carried out by bringing the fusible material to atemperature of between about 335 and about 380 degrees Celsius;specifically, between about 350 and about 370 degrees Celsius. The moldmay then be cooled and optionally quenched until the temperature of themold drops to about 250 degrees Celsius. The mold may optionally furtherbe quenched (for handling reasons) with ambient temperature fluid suchas water. Thereafter, the two halves 91 and 100 of mold 90 can be pulledapart, and the graft assembly removed.

The use of mold 90 to facilitate the inflatable channel expansion andsintering process is unique in that the mold cavity portion 93 acts as abackstop to the graft body section so that during sintering, thepressure created by the injected fluid that tends to expand theinflatable channels outward is countered by the restricting pressureexerted by the physical barrier of the surfaces defining the mold cavity93. In general terms, therefore, it is the pressure differential acrossthe inflatable channel ePTFE layers that in part defines the degree ofexpansion of the channels during sintering. During the sintering step,the external pressure exerted by the mold cavity surface competes withthe fluid pressure internal to the inflatable channels (kept at a levelto counteract any leakage of fluid through the ePTFE pores at sinteringtemperatures) to provide an optimal pressure differential across theePTFE membrane(s) to limit and define the shape and size of theinflatable channels.

Based on this concept, we have found it possible to use alternatives toa mold in facilitating the inflatable channel expansion process. Forinstance, it is possible inject the channel network with a working fluidthat does not leak through the ePTFE pores and to then expand thenetwork during sintering in a controlled manner, without any externalconstraint. An ideal fluid would be one that could be used within thedesired ePTFE sintering temperature range to create the necessarypressure differential across the inflatable channel membrane and theambient air, vacuum, or partial vacuum environment so to control thedegree of expansion of the channels. Ideal fluids are those that possessa high boiling point and lower vapor pressure and that do not react withePTFE, such as mercury or sodium potassium. In contrast, the network ofinflatable channels 84 can also be expanded during the fixation processor sintering process by use of vapor pressure from a fluid disposedwithin the network of inflatable channels 84. For example, the networkof inflatable channels 84 can be filled with water or a similar fluidprior to positioning assembly in the oven, as discussed above. As thetemperature of the graft body section 15 and network of inflatablechannels 84 begins to heat, the water within the network of inflatablechannels 84 begins to heat and eventually boil. The vapor pressure fromthe boiling water within the network of inflatable channels 84 willexpand the network of inflatable channels 84 provided the vapor isblocked at the inflation line 85 or otherwise prevented from escapingthe network of inflatable channels.

FIG. 18 shows an elevational view in partial longitudinal section of anendovascular graft assembly 105 manufactured by the methods and with theapparatus described above. Endovascular graft assembly 105 comprises agraft body section 108 with a proximal end 106, a distal end 107, andcircumferentially oriented inflatable channels 111 shown in an expandedstate. A longitudinal inflatable channel 116 fluidly communicates withthe circumferential inflatable channels 111.

An expandable member in the form of a proximal connector member 112 isshown embedded between proximal end wrap layers 113 of fusible material.An expandable member in the form of a distal connector member 114 islikewise shown embedded between distal end wrap layers 115 of fusiblematerial. The proximal connector member 112 and distal connector member114 of this embodiment are configured to be secured or connected toother expandable members which may include stents or the like, which arenot shown. In the embodiment of FIG. 18, such a connection may beaccomplished via connector elements 117 of the proximal and distalconnector members 112 and 114, which extend longitudinally outside ofthe proximal and distal end wrap layers 113 and 115 away from the graftbody section 108.

The FIG. 18 embodiment of the present invention features junction 118between the distal end wrap layers 115 of fusible material and thelayers of fusible material of a distal end 121 of the graft assemblymain body portion 122. There is likewise a junction 123 between theproximal end wrap layers 113 and the layers of fusible material of aproximal end 124 of the graft assembly main body portion 122. Thejunctions 118 and 123 may be tapered, with overlapping portions that arebound by sintering or thermomechanical compaction of the end wrap layers113. and 115 and layers of the main body portion 122. This junction 123is shown in more detail in FIG. 19.

In FIG. 19, six proximal end wrap fusible material layers 113 aredisposed between three fusible material inner layers 125 and threefusible material outer layers 126 of the main body portion proximal end124.

FIG. 20 illustrates a sectional view of a portion of the distalconnector member 114 disposed within the distal end wrap layers 115 offusible material. Connector member 114 is disposed between three outerlayers 127 of fusible material and three inner layers 128 of fusiblematerial. Optional seams 127A, formed by the methods discussed above,are disposed on either side of distal connector member 114 andmechanically capture the connector member 114. FIG. 21 likewise is atransverse cross sectional view of the proximal connector member 112embedded in the proximal end wrap layers 113 of fusible material.

FIG. 22 illustrates a transverse cross section of the longitudinalinflatable channel 116 formed between main body portion 122 outer layers131 and the main body portion 122 inner layers 132. FIG. 23 is atransverse cross section of graft main body portion 122 showing acircumferential inflatable channel 111 in fluid communication withlongitudinal inflatable channel 116. The circumferential inflatablechannel 111 is formed between the outer layers 131 of fusible materialof main body portion 122 and inner layers 132 of fusible material ofmain body portion 122.

FIG. 24 shows an alternate embodiment of an interior surface supportmeans in the form of an elongate mandrel 150 for shape forming anendovascular graft or section thereof. The mandrel 150 has an outersurface contour 151 configured to support an inside surface of an graftsection and is substantially cylindrical in configuration. The mandrel150 has a middle section 152 with a first end 153 and a second end 154.Additionally, a mandrel first end section 155 is disposed at first end153 of middle section and a mandrel second end section 156 is disposedat second end 154 of middle section 152. First and second end sections155 and 156 typically have an outer transverse dimension, at least aportion of which is larger than the outer transverse dimension of middlesection 152. First end section 155 is removably secured to the first end153 of middle section 152 by threaded portion 157. Alternatively, firstend section 155 may be removably secured by any other suitable mechanismor means such as attached by set screws, interlocking mechanisms or thelike. In some embodiments second end section 156 may be removablyattached, to second end 154 of the shape forming mandrel 150 by threadedportions 158 or alternate securement mechanisms. Middle section 152 ofmandrel 150 will typically range in length from about 50 to about 150mm, specifically from about 75 to about 100 mm, and typically has anouter transverse dimension from about 5 to about 50 mm; specificallyfrom about 15 to about 25 mm. Typically first and second end sections155 and 156 may have a tapered portion 161 and 162 adjacent first andsecond ends 153 and 154 of middle section 152, respectively. First endsection 155 is substantially cylindrical in configuration and typicallyhas an outer transverse dimension of about 15 to about 40 mm, such asabout 20 to about 30 mm. Second end section. 156 may have a similarconfiguration. Typically middle section 152, first end section 155 andsecond end section 156 are substantially circular or elliptical in shapeand cross section. They may be comprised of stainless steel but they mayalso be comprised of other metal alloys and materials such as aluminum,titanium, nickel-based alloys, ceramic materials, etc. In the embodimentof FIG. 24, middle section 152, first end section 155 and second endsection 156 are substantially coaxial over a longitudinal axis.

A pressure line recess 163 in the form of a longitudinal channel isformed in the outer surface 151 of the middle section 152 which isconfigured to accept a pressure line (not shown). The longitudinalchannel or pressure line recess 163 is typically semicircular orc-shaped in transverse cross section as shown in FIG. 25 and has aradius of curvature ranging from about 0.005 to about 0.090 inch. Thepressure line recess 163 extends along the middle section 152 of mandrel150 and terminates at first and second end sections 155 and 156.Alternate embodiments of the present invention include a pressure linerecess 163 that extends along the first or second end sections 155 and156.

Referring now to FIGS. 27–29, an outer constraint means in the form of amold 165 for the manufacture of an endovascular graft, or sectionthereof, is shown. The mold 165 is configured for the manufacture of agraft section which has at least one inflatable channel or inflatablecuff and can have the same or similar features as the mold 90 shown inFIGS. 16A–16C and 17 above. A first mold body portion 166 has a proximalend 167, a distal end 168 and is configured to mate with a second moldbody portion 171 shown in FIG. 29. The first mold body portion 166 andsecond mold body portion 171 each has a main cavity portion 172 and 173,respectively, formed into the respective mold body portions 166 and 171.Main cavity portions 172 and 173 have inside surface contours 174 and175, respectively, that are configured to correspond to an outsidesurface contour of a graft section with the inflatable channels or cuffsin an expanded state. Circumferential channel cavities 176 are disposedon the inside surface contours 174 and 175 of main cavity portions 172and 173 and are configured to accept circumferential inflatable channelsof an endovascular graft or graft section. Circumferential inflatablecuff cavities 177 are disposed on the inside surface contours 174 and175 of the main cavity portions 172 and 173 near or adjacent a firsttapered portion 178 and second tapered portion 179 of the main cavityportions 172 and 173. First tapered portion 178 of main cavity portions172 and 173 is disposed adjacent the proximal end 167 of mold 166.Second tapered portion 179 of main cavity portions 172 and 173 isdisposed adjacent the distal end 168 of mold as shown in FIG. 28.

First mold body portion 166 has a contact surface 181 that is configuredto mate with a contact surface 182 of the second mold body portion 171.The contact surface 182 of the second mold body portion 171 in FIG. 29has a plurality of exhaust channels 183 formed in the contact surface182 thereof; extending from main cavity portion 173 to a positionoutside mold 165. Exhaust channels 183 allow pressurized gas or othermaterial to escape from main cavity portion 172 and 173 of the moldduring inflation of the inflatable channels and cuffs. In the embodimentof FIG. 29, exhaust channels 183 are formed, or cut, in contact surface182 of the second mold body portion 171 only and are configured tolongitudinally align with the inflatable cuff cavities 177 andinflatable channel cavities 176 of the main cavity portion 173 of themold body portion 171, respectively. The longitudinal alignment ofexhaust channels 183 with the inflatable channel and cuff cavities 176and 177 provides for more efficient expansion of the inflatable channelsand cuffs. The exhaust channels 183 allow for a greater pressuredifferential between an inside volume of inflatable cuffs and channelsdisposed within the cavities 176 and 177 and a volume between an outsidesurface of the inflatable cuffs and channels and inside surface of themold 165 during inflation.

The mold 165 shown in FIGS. 27–29 includes two mold body portions 166and 171; however, other embodiments may include a plurality of mold bodyportions with at least one of the mold body portions configured to matewith at least one of the other mold body portions to form an assembledmold having a main cavity portion. The main cavity has an inside surfacecontour that matches an outside surface contour of the endovasculargraft, or section thereof, with at least one inflatable channel or cuffof the graft section in an expanded state. Such embodiments may havethree, four, five or more mold body portions configured to mate witheach other as described above. In some configurations, even a singlemold body portion can be used.

With the mold 165 assembled, main cavity portions 172 and 173 typicallyextends along the length of each mold body portion 166 and 171 and havea length of about 50 to 400 mm, specifically about 100 to about 180 mm.The main cavity portions 172 and 173 typically have an inner transversedimension of about 3 to 50 mm. Mold body portions 166 and 171 may becomprised of a sintered metal material such as stainless steel or anyother suitable material such as aluminum. Exhaust channels 183 may beunnecessary in a mold embodiment made of sintered metal because theporous nature of sintered metal allows gas to escape from any portion ofthe closed sintered metal mold.

Another embodiment may include a mold body portion having a main cavityportion with at least one longitudinal channel cavity disposed on theinside surface contour of a mold main cavity portion, and extendinglongitudinally along the inside surface contour. The longitudinalchannel cavity can have an inside surface contour that corresponds to anoutside surface contour of an inflatable longitudinal channel of anendovascular graft as shown in FIG. 34 in an expanded state. Anotherembodiment may have one or more mold body portions which have at leastone helical channel cavity disposed on the inside surface contour of themold main cavity portion. The helical channel cavity may have an insidesurface contour that corresponds to an outside surface contour of aninflatable helical channel of the endovascular graft in an expandedstate as shown in FIG. 39.

One of the difficulties encountered in expanding the graft sectioninflatable channels and cuffs derives from the porosity of the flexiblematerial that may be used for the graft body section, For example if aporous flexible material such as ePTFE is used for the graft bodysection, the pressure of pressurized fluid such as a gas injected froman inflation port will decrease with increasing distance from theinflation port as the gas escapes through the porous material. This canresult in a graft section with inflatable channels and cuffs which areinconsistently inflated and fixed. FIG. 30 depicts a pressure line 190for use in the manufacture of an endovascular graft or section thereofwhich allows for a substantially even distribution of pressure within anetwork of inflatable channels and cuffs during inflation and fixing ofthe inflatable channels and cuffs.

The pressure line 190 shown is an elongate gas containment means in theform of an elongate conduit 191 with a length of about 2 to about 12inches. The elongate conduit 191 has a proximal end 192, a distal end193, a proximal section 194 and a distal section 195. Note theconvention used herein where the distal end 193 of conduit 191 will bedisposed at the proximal end of graft body section.

A means for producing a permeability gradient in the form of a permeablesection 196 is disposed along the conduit distal section 195. Typicallydisposed at the pressure line proximal end 192 is an adapter or fitting197 such as a Luer adapter which has an, input port 198. Pressurizedfluid (gas and/or liquid) may be injected into pressure line 190 throughinput port 198. The permeable section 196 has a plurality of orifices201 disposed therein which generally increase in diameter with anincrease in distance from the proximal end 192, resulting in apermeability, gradient which increases in distance from the conduitproximal end 192. The distal end or extremity 193 of the pressure line190 can have a distal port (not shown) in addition to the plurality ofoutlet orifices 201 but may alternately be closed or partially closed.

Proximal section 194 of elongate conduit 191 is typically comprised ofstainless steel but may alternately be comprised of materials and metalssuch as aluminum, titanium, nickel-based alloys, ceramic materials,brass, etc. as well as polymeric tubing such as polyimide. Proximalsection 194 generally is cylindrical in transverse cross section asshown in FIG. 31. The proximal section 194 has an angled step downportion 202 with first and second bends 203 and 204 respectively,configured to mate with the mandrel tapered portion 161 or 162 as shownin FIG. 24. Angled step down portion 202 can conform to a taperedconfiguration of a graft or graft and mandrel assembly in which thepressure line 190 is placed on mandrel 150 during the formation of anendovascular graft body section. Step down portion 202 may be D-shapedin transverse cross section, which allows a more streamlined profile foraccommodation of the pressure line 190 within the endovascular graft orgraft assembly. Step down portion 202 may form an angle of about 2 toabout 30 degrees with respect to a longitudinal axis 205 of a distalsection of the elongate conduit 191.

Distal to step down portion 202, proximal section 194 is D-shaped intransverse cross section as shown in FIG. 32 and extends toward thedistal section 195. The flat portion 206 of the D-shaped cross sectionallows the pressure line 190 to have a lower profile when lying on asurface such as the outside surface of the tapered portion 161 or 162 ofa shape forming mandrel 150.

Distal section 195 has an elongate tubular configuration and issealingly secured to proximal section 194 at a junction 207. Distalsection 195 nominally has a circular transverse cross section and mayhave an outer transverse dimension of about 0.01 to about 0.1 inch;specifically, about 0.025 to about 0.035 inch. Distal section 195 isformed of a high durometer polymer such as polyimide or the like,although other suitable materials such as stainless steel may be used.The distal section 195 can be D-shaped along a proximal portion 208thereof when compressed within a distal portion 209 of the proximalsection 194 as shown in the transverse cross sectional view of FIG. 32.

The permeable section 196 has a proximal end 211 and a distal end andextends proximally from the distal end 193 of the pressure line 190 forthe embodiment shown in FIG. 30. The permeable section 196 has aplurality of outlet orifices 201 which increase in diameter toward thedistal end 193 of the pressure line 190. In one embodiment of thepressure line 190, the orifice or orifices 201 of the permeable section196 have increased area relative to the area of orifices disposedproximally thereof. In such an embodiment, the smallest and mostproximal orifices 213 may have a diameter of about 0.002 to about 0.007inch and the largest orifices 214 adjacent the distal end 212 of thepermeable section 196 may have a diameter of about 0.018 to about 0.022inch. The varied area of the orifices 201 provides for an increase inpermeability distally, which results in a predetermined permeabilitygradient that may be designed or adjusted to alleviate inconsistentexpansion of the inflatable channels and cuffs of a graft section. Thispermeability gradient may increase from about 5 to about 20 percent percentimeter along a direction from the proximal end 211 of permeablesection 196 to the distal end 212 of permeable section 196 in someembodiments.

Orifices 201 may be longitudinally spaced along the permeable section196 so that each opening or orifice 201 corresponds to a givenlongitudinal spacing and position of circumferential, helical, or othertypes of inflatable channels or cuffs of an endovascular graft or graftsection. Alignment of the orifices 201 with the inflatable channels orinflatable cuffs of a graft section can provide for a consistent andefficient inflation of the inflatable channels with fluid (liquid orgas) as it travels longitudinally along pressure line 190 and maintainsa constant pressure throughout as it fills the inflatable channels andcuffs. In addition, although the embodiment of pressure line 190 of FIG.30 is shown with a permeable section 196 formed by a plurality oforifices 201, other configurations may be used. For example, permeablesection 196 could be made from a porous material such as sintered metalor a porous polymer, wherein the porosity increases over a longitudinallength of the permeable section 196 in order to produce a desiredpermeability gradient over the length of permeable section 196.

FIG. 34 is a top view of an endovascular graft assembly 221 disposedabout an interior surface support means in the form of a shape formingmandrel 222 and disposed within the main cavity portion 172 of firstmold body portion 166. The second mold body portion 171 of mold 165 isnot shown for the purpose of clarity of illustration. The embodiment ofthe shape forming mandrel 222 may have the same or similar features tothe mandrel 150 shown in FIG. 24. The embodiment of the endovasculargraft assembly 221 of FIG. 34 may have the same or similar features tothe endovascular graft assembly 105 of FIG. 18 discussed above.

The endovascular graft assembly 221 has a graft body section 223 havinga proximal end 224, a distal end 225, and a plurality of circumferentialinflatable channels 226 and inflatable cuffs 227 in fluid communicationwith a longitudinal inflatable channel or spine 228. An inflation port231 is disposed at the distal end 225 of the graft body section 223 andis in fluid communication with the longitudinal inflatable channel 228.Pressure line 190 is disposed within inflation port 231 and longitudinalinflatable channel 228, with the inflatable channels 226 of the graftbody section 223 in an unexpanded or collapsed state. The pressure line190 extends from the inflation port 231 to a proximal inflatable cuff232.

FIG. 35 is a transverse cross sectional view of the graft body section223, mandrel 222 and pressure line 190 and FIG. 36 is an enlarged viewof the circled portion of FIG. 35.

Referring to FIG. 36, pressure line 190 is shown disposed within thelongitudinal inflatable channel 228, which is disposed between outerlayers of flexible material 233 and inner layers of flexible material234 of graft body section 223. The inner layers of flexible material 234and outer layers of flexible material 233 are sealed together at a firstseam 235 and a second seam 236 which serve to form and definelongitudinal inflatable channel 228.

FIG. 37 is an enlarged view of the circled portion of FIG. 34 with thegraft body section 223 partially cut away for the purpose ofillustration. Pressure line 190 is positioned such that permeablesection 196 of pressure line 190 is disposed within the longitudinalinflatable channel 228 with the outlet orifices 201 aligned with and influid communication with the circumferential inflatable channels 226 andcircumferential inflatable cuffs 227 of graft body section 223.Additionally, circumferential inflatable channels 226 of the graft,pictured in a noninflated collapsed state, are substantially alignedwith and disposed adjacent corresponding circumferential channelcavities 176 of mold body portion 166.

Once pressure line 190 has been properly positioned within thelongitudinal inflatable channel 228 of graft body section 223,pressurized fluid, typically a gas, or other material may be injectedinto the network of inflatable channels and cuffs 237. The injection ofpressurized gas into the network of inflatable channels and cuffs 237forces flexible material 233 of the inflatable channels and cuffs 226and 227 to expand radially outward as indicated by the arrows 238 inFIG. 37. A more detailed illustration and description of this radialoutward expansion of the flexible material 233 may be found in FIG. 17and its corresponding discussion. The permeability gradient of thepermeable section 196 may be chosen so that the pressure and mass flowof pressurized gas exiting the outlet orifice 213 at the permeablesection proximal end 211 is substantially the same as the pressure andmass flow of pressurized gas exiting the outlet orifice 214 at thepermeable section distal end 212. This ensures that the inflatable cuff232 at the proximal end 224 of graft body section 223 will havesubstantially the same amount of inflation as the inflatable cuff 239 atthe distal end 225 of graft body section 223.

The pressure gradient may be configured such that the gas pressure atthe circumferential inflatable channels 226 (disposed between theinflatable cuffs 227) will receive substantially the same pressure aswell. It should be noted that in some embodiments of graft body sections223, inflatable cuffs 227 may have a larger volume than adjacentinflatable channels 226. Therefore, inflatable cuffs 227 may requiremore mass flow from a corresponding outlet orifice 201 than the massflow from an outlet orifice 201 corresponding to a circumferentialinflatable channel 226 in order to maintain the same pressure.

As the pressurized gas forces the flexible material 233 of thecircumferential inflatable channels 226 and inflatable cuffs 227radially outward, the radial outward movement of the material 233 isultimately checked by the inside surface contour 174 of thecircumferential channel cavities 176 and cuff cavities 177. Inwardradial movement or displacement of flexible material 233 is prevented byan outside surface 241 of mandrel 222. FIG. 38 shows the circumferentialinflatable channels 226 and inflatable cuffs 227 of graft body section223 in an expanded state. This allows the circumferential inflatablechannels 226 and inflatable cuffs 227 to be formed and then fixed byfixing the flexible material 233 and 234 of the inflatable channels andcuffs 226 and 227 while in an expanded state. As discussed above, if theflexible material is ePTFE, the flexible material may be fixed by asintering process.

For some non-bifurcated embodiments of graft body sections 223,pressurized gas may be injected at a rate of about 2 to about 15 scfh;specifically, about 5 to about 6 scfh. For such embodiment, the pressureof the pressurized gas can be from about 5 to about 30 psi. For somebifurcated embodiments of graft body sections 223, pressurized gas mayinjected at a rate of about 15 to about 30 scfh; specifically, about 18to about 20 scfh. For such bifurcated embodiments, the pressure of thepressurized gas can be from about 15 to about 60 psi. In anotherembodiment, the rate at which pressurized gas is injected into theinflatable channel and cuff network 237 of the graft body section 223may be normalized based on the surface area of that portion ofendovascular graft body section 223 that is being expanded.

For some graft body section 223 embodiments, there is no permanentlongitudinal inflatable channel 228. For these embodiments, it may bedesirable to include a temporary longitudinal inflation-channel in thegraft body section in order to provide access to the inflatable channelsof the graft body section for injection of pressurized gas FIG. 39 showsa graft section 250 disposed within a mold body portion 251 having aproximal inflatable cuff 252, distal inflatable cuff 253, helicalinflatable channel 254 and temporary longitudinal inflatable channel255. The temporary longitudinal inflatable channel 255 is in fluidcommunication with proximal inflatable cuff 252, distal inflatable cuff253 and helical inflatable channel 254. A pressure line 256 is disposedwithin the temporary longitudinal inflatable channel 255 and has outletorifices 257 that are aligned with and correspond to the proximalinflatable cuff 252, distal inflatable cuff 253 and helical inflatablechannel 254. The inflatable channel 254 and cuffs 252 and 253 are shownin an expanded state. Outlet orifices 257 may be configured to produce apressure gradient that evenly distributes appropriate mass flow from thepressure line 256 to the inflatable cuffs 252 and 253 and inflatablehelical channel 254.

Once the flexible material of the inflatable channel and cuffs 252, 253and 254 is fixed while the inflatable channel and cuffs 254, 252 and 253are in the expanded state, pressure line 256 may be removed and thetemporary longitudinal inflatable channel 255 sealed in desired portions258 so as to leave the inflatable cuffs 252 and 253 and inflatablehelical channel 254 patent. Sealed portions 258 of the temporarylongitudinal inflatable channel 255 shown in FIG. 40 are formed bypressing the layers of flexible material 259 at the sealed portionslocations flat together and forming an adhesion by adhesive bonding,thermomechanical sealing or any other suitable method. A suitablematerial that may be used to seal the sealed portion of the temporarylongitudinal inflatable channel 255 is FEP; however, any other suitablematerial such as silicone elastomer may be used. It may be desirable touse an adhesion method for the sealed portions 258 that maintains a lowprofile and high degree of flexibility of the sealed portions of thetemporary longitudinal inflatable channel 255.

FIG. 41 illustrates another embodiment of a graft body section 261having no permanent longitudinal inflatable channel. A temporarylongitudinal inflation channel 262 in the graft section 261 providesaccess to the circumferential inflatable channels 263 and thelongitudinal inflatable channel segments 264 of the graft section 261for injection of pressurized gas. FIG. 41 shows graft section 261disposed within a mold body portion 265 and having a proximal inflatablecuff 266, distal inflatable cuff 267, circumferential inflatablechannels 263, longitudinal inflatable channel segments 264 and temporarylongitudinal inflatable channel 262. Temporary longitudinal inflatablechannel 262 is in fluid communication with the other inflatable cuffsand channels 266, 267, and 263. A pressure line 268 is disposed withinthe temporary longitudinal inflatable channel 262 and has outletorifices 269 that are aligned with and correspond to the proximalinflatable cuff 266, distal inflatable cuff 267 and circumferentialinflatable channels 263. The inflatable channels 263 and cuffs 266 and267 are shown in an expanded state. Outlet orifices 269 may beconfigured to produce a pressure gradient that evenly distributespressure and appropriate mass flow from pressure line 268 to inflatablecuffs 266 and 267 and inflatable circumferential channels 263.

Once a flexible material 270 of the inflatable channels 263 and cuffs266 and 267 are fixed while the inflatable channels 263 and cuffs 266and 267 are in the expanded state, pressure line 268 may be removed, andthe temporary longitudinal inflatable channel 262 may be sealed indesired portions 271 so as to leave the inflatable cuffs 266 and 267 andinflatable channels 263 patent. Sealed portions 271 of temporarylongitudinal inflatable channel 262 shown in FIG. 42 may be formed in amanner similar to the sealed portions 258 of the temporary longitudinalinflatable channel 255 of FIG. 40.

While particular forms of embodiments of the invention have beenillustrated and described, it will be apparent that variousmodifications can be made without departing from the spirit and scope ofthe invention. Accordingly, it is not intended that the invention belimited, except as by the appended claims.

1. An assembly for manufacture of an endovascular graft or section thereof which has at least one inflatable cuff or channel on the graft section, comprising: a) a mandrel comprising an elongate body having an outer surface contour configured to support an inside surface of the endovascular graft; b) the graft section having at least one inflatable cuff or channel disposed about at least a portion of the mandrel; c) a pressure line comprising an elongate conduit having an input end, an output end and a permeability gradient which increases with distance from the input end and which is in fluid communication with an inflatable cuff or channel of a main body portion of the endovascular graft; d) a mold at least partially disposed about the graft section, the pressure line and the mandrel, comprising a plurality of mold body portions configured to mate together to produce an assembled mold having a main cavity portion with an inside surface contour that matches an outside surface contour of the graft section with the at least one inflatable cuff or channel in an expanded state and configured to radially constrain an outer layer or layers of the at least one inflatable cuff or channel during expansion of the cuff or channel.
 2. The assembly of claim 1 wherein the pressure line is at least partially disposed within an inflatable cuff or channel of the graft.
 3. The assembly of claim 2 wherein the permeability gradient of the pressure line results from a plurality of orifices disposed in the elongate conduit which increase in diameter as distance from the input end of pressure line increases.
 4. The assembly of claim 3 wherein the plurality of orifices are substantially aligned with circumferential channel cavities of the mold.
 5. The assembly of claim 1 wherein the mandrel comprises a middle section; a first end section with at least a portion that has a larger outer transverse dimension than an outer transverse dimension of the middle section and which is removably secured to a first end of the middle section; and a second end section disposed at a second end of the middle section with at least a portion that has a larger outer transverse dimension than an outer transverse dimension of the middle section.
 6. The assembly of claim 5 wherein the mandrel further comprises a pressure line recess that includes a longitudinal groove formed in an outer surface of the mandrel.
 7. The assembly of claim 3 wherein the orifices of the pressure line are substantially aligned with inflatable channels of the main body portion.
 8. An assembly for manufacture of an endovascular graft or section thereof which has at least one inflatable cuff or channel on a graft section, comprising: a) an interior surface support means configured to support an inside surface of the graft section; b) the graft section having at least one inflatable cuff or channel disposed about at least a portion of the interior surface support means; c) a pressure line comprising an elongate gas containment means having an input end, an output end and means for producing a permeability gradient which increases with distance from the input end along a section of the elongate gas containment means; d) an outer constraint means at least partially disposed about the graft section, the pressure line and the interior surface support means, comprising a plurality of outer constraint body means configured to mate with at least one of the other outer constraint body means to produce an assembled outer constraint means configured to radially constrain an outside surface contour of the graft section with the at least one inflatable channel or cuff in an expanded state during expansion of the cuff or channel. 